模態分析於平板聲輻射主動控制之應用

Applications of Modal Analysis to Active Control of Sound by Plates

林文弘(Wen-Hong Lin)

指導教授 ： 陳國在

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.02391

摘要

本論文討論的主題為對一由壓電片激振之四邊固定矩形平板所產生的聲輻射作主動控制。
首先，本文分析了平板的運動機制，並從輻射模態的觀點計算平板的輻射聲必v。理論上聲必v是由各輻射模態貢獻量疊加而得。由數值計算可發現，不同位置的激振點會激發出相異之輻射模態貢獻量分佈狀況。因而可利用此一特性控制不同輻射模態的聲必v，增加平板輻射聲必v的衰減量。
實驗部分，本論文使用了兩個獨立的控制系統。第一個控制系統是將壓電片置於平板角落，並使用小塊壓電片量取平板表面的振動訊號作為參考誤差。另一個則是將壓電片置於中央，使用麥克風量取聲壓做為參考誤差。在之前的研究中，使用麥克風並以中央的壓電片作控制點的安排成它a降低了第一輻射模態的聲必v。其他輻射模態則可藉由適當選取量取振動點的位置來達成聲必v的衰減。
實驗結果顯示了低頻時本論文的機制較單一控制器對聲必v的抑制效果為佳。

關鍵字

模態分析 ； 輻射模態 ； 主動控制

並列摘要

Active control of sound radiation from a vibrating clamped rectangular plate excited by a steady state harmonic PZT is experimentally studied.

First, the mechanism of vibrating plate is analyzed numerically. Then the sound power is calculated by summing individual contributions of radiation modes. From the numerical results, different locations of exciting points will have various radiation mode distribution patterns. Thus, it is possible to reduce more sound power by arranging the locations of controlling points to attenuate individual radiation modes.

For simplicity, the experiment of this study employs two independent control systems. The first one has a PZT attached to the corner of the plate with a piezoceramic patch as error sensor of vibration. And another PZT is attached to the center of the plate, with a microphone in the radiation field as error sensor of sound pressure. In recent researches, this arrangement of PZT at the center with microphone successfully reduces the sound power of first radiation mode. And the power of other modes can be attenuated by carefully choosing the location of piezoceramic patch error sensor.

The experiment results show that this control strategy reduces more sound power than a single control system in lower frequencies.

並列關鍵字

Active Control ； Radiation Mode ； Moda Analysis

參考文獻

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